JPH1020223A - Cylinder inner surface scanning type image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate mechanical adjustment so as to improve accuracy and to constitute an entire recorder to be compact by making a movable part as a scanning means. SOLUTION: A spinner SP functioning as an optical scanner is provided on the center axis of a drum, has a reflection surface set at 45 deg. with respect to the center axis, and is rotated by a motor at high speed. Three laser beams L on/off controlled in accordance with image information and outputted from a laser diode 6 functioning as a light beam output means are deflected in an X-axis direction by acoustooptical elements AODa to AODc . After the three laser beams are multiplexed by a multiplexing optical element 8, they are introduced into the spinner SP being the optical scanner through a condensing lens L6. The spinner SP reflects and deflects a laser beam L0 by the reflection surface rotating centering a Z-axis and guides it to a recording sheet. In such a case, since a rotating component element is only the spinner SP, the accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical inner surface scanning type image recording apparatus which scans a recording sheet held on an inner surface of a cylinder with a plurality of light beams modulated according to image information and records an image. It is.

[0002]

2. Description of the Related Art Conventionally, there are the following three types of apparatuses for recording an image on a recording sheet using a laser beam. The first apparatus is a flat-scanning image recording apparatus that performs recording by irradiating a flat recording sheet conveyed in the sub-scanning direction with a laser beam in the main scanning direction. The second device is a cylindrical outer surface scanning type image recording device that performs recording by irradiating a laser beam onto a recording sheet attached to the outer peripheral surface of a rotating drum. The third device is a cylindrical inner surface scanning type image recording device that performs recording by irradiating a recording sheet adhered to the inner surface of the cylinder with a laser beam from inside the inner cylinder.

[0003] In the cylindrical inner surface scanning type image recording apparatus, for example, a laser beam is incident along the central axis of the cylinder, and the reflecting surface is set at approximately 45 ° with respect to the incident direction, that is, the central axis direction of the cylinder. The optical scanner is arranged on the central axis of the cylinder, and the laser beam is scanned (main scanning) on the recording sheet by rotating the reflection surface about the central axis. The optical scanner is moved in the central axis direction (sub-scanning direction) with the rotation.

In this cylindrical inner surface scanning type image recording apparatus, since the recording sheet is adhered to the inner surface of the cylinder, the recording sheet does not peel off during recording, the dimensional accuracy of the recorded image is high, and the recording speed is high. Due to their excellent scanning properties and economical efficiency, they have been widely used in recent years. For example, it is often used in photolithography to form an image on a PS plate (Pre-Sensitized Plate).

[0005] In the meantime, in the cylindrical inner surface scanning type image recording apparatus configured as described above, an attempt has been made to improve the recording speed by performing scanning using a plurality of laser beams. In this case, simply inputting a plurality of laser beams to the optical scanner cannot linearly scan the laser beam on the recording sheet, so that accurate image recording cannot be performed.

FIG. 17 is a perspective view of the vicinity of an optical scanner for explaining that linear scanning cannot be performed, and FIG. 18 is a developed view of scanning lines as an output result of the main scanning. In FIG. 17, reference numeral 2 denotes an optical scanner, the rotation axis of which is located on the central axis of the recording sheet S wound in a cylindrical shape. The center axis is the Z axis, and the orthogonal coordinate system formed by the right thumb, index finger, and middle finger is the X, Y, and Z axes.

Here, three laser beams # 1, # 2,
# 3 is on the YZ plane and is parallel to the Z axis. The center laser beam # 2 is incident on the Z-axis, and the reflection surface 4 of the optical scanner 2 is such that the intersection of its long axis and short axis is at the origin of the XYZ coordinate system. I do. The reflecting surface 4 has a 45 ° inclination with respect to the Z axis.

When the reflecting surface 4 of the optical scanner 2 is in the direction shown in FIG. 17A (the direction in which the short axis of the reflecting surface 4 coincides with the Y axis),
The three laser beams # 1, # 2, and # 3 incident parallel to and aligned on the short axis of the reflection surface 4 in a state parallel to the Z axis are reflected along the XY plane, and each of the laser beams # 1 , # 2, # 3
Arrives at the recording sheet S while traveling on the same scanning line. When the reflection surface 4 is rotated by 90 ° from the state shown in FIG. 17A and turned to the direction shown in FIG. 17B, the recording sheet is separated in the state where the laser beams # 1, # 2, and # 3 are separated in the Z-axis direction. Reach S.

Further, the reflection surface 4 is shifted from the state shown in FIG.
When rotated by 0 ° and turned to the direction of FIG. 17C, the laser beams # 1, # 2, and # 3 are reflected again along the XY plane, and the respective laser beams # 1, # 2, and # 3 arrives at the recording sheet S while traveling on the same scanning line. In this case, since the positions of the incident laser beams # 1, # 2, and # 3 on the reflection surface 4 fluctuate according to the rotation angle of the optical scanner 2, the laser beams # 1, # 2, and # 3 are incident on the recording sheet S at the center of the reflection surface 4. 1 except for the scanning line formed by the laser beam # 2.
As shown in FIG. 8, a curved scanning line is formed.

Various methods have been proposed in the past to avoid the above-mentioned problems that occur when scanning is performed using a plurality of laser beams. For example, by disposing a hologram that rotates together with the optical scanner between the light source of the laser beam and the optical scanner, and by controlling the diffraction angle according to the incident position of the laser beam on the hologram, the optical scanner There is a configuration in which the incident position of a laser beam is adjusted so that each scanning line on a recording sheet is linear as a result (Japanese Patent Publication No. 4-73829).

Further, two laser beams of P-polarized light and S-polarized light are generated, one of these laser beams is guided to a recording sheet via a rotating deflection beam splitter, and the other is separated by the deflection beam splitter. There is a configuration in which a laser beam is guided to the recording sheet via a rotating reflecting plate (Japanese Patent Laid-Open No. 5-2718).
No. 8).

Further, when each of the two laser beams of P-polarized light and S-polarized light is modulated based on an image signal, the laser beam is guided onto a recording sheet via a rotating hologon (hologram diffraction grating) deflector for scanning. There is a configuration in which one laser beam is deflected by a mirror whose angle is controlled by a piezo element in accordance with the rotation angle of the hologon deflector to maintain the interval between two scanning lines (US Patent No. 5,097,351).

Further, there is an optical scanner in which a laser beam is reflected three times to guide the laser beam to a recording sheet, and the optical scanner is rotated so as to eliminate the twist of the laser beam (Japanese Patent Laid-Open No. Hei 5 (1993)). -27190, JP-A-5-289018, JP-A-5-308488).

Further, there is a light emitting element array for outputting a plurality of light beams, which is rotatably arranged on the center axis of a cylinder, and which is configured to rotate the light emitting element array (JP-A-5-639).
No. 20).

Further, a transparent medium layer is provided on the reflecting surface of the rotating optical scanner, a plurality of laser beams having different wavelengths are made incident on the transparent medium layer, and the laser beams are separated using a difference in refractive index. There is one configured to be guided on a recording sheet (JP-A-4-348311, JP-A-6-34831).
No. 95016, hereinafter referred to as a method using a transparent medium).

Accordingly, the applicant of the present application has positioned one laser beam # 2 of the plurality of laser beams on the rotation axis of the optical scanner 2 in FIG. , # 3 to one-dimensionally deflect the scanning lines. It has also been proposed to deflect the two laser beams # 1 and # 3 two-dimensionally to prevent the scanning line from being curved and to correct the interval and length between these three laser beams (Japanese Patent Application No. Hei 10-26138). 6-213773, 6-213772, 7
No. 113328, U.S. Pat. No. 5,502,709, hereinafter referred to as a method already proposed by the same applicant).

[0017]

However, in these prior arts, the methods other than the method of providing the transparent medium layer and the last method already proposed by the same applicant have to be rotated together with the optical scanner. Therefore, there is a problem that accuracy is reduced and the configuration is complicated. According to the last method, the structure is relatively simple, but the wavelength is extremely difficult to manage, so that the width of the scanning line on the recording sheet cannot be adjusted accurately.

In the method of US Pat. No. 5,097,351, the interval between two scanning lines can be fixed, but the scanning position of the two scanning lines in the main scanning direction is set. The adjustment is not specifically described, so that high-precision image recording cannot be performed.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 5-27188 and US Pat. No. 5,097,351,
Since only two laser beams can be controlled, the number of laser beams cannot be increased to three or more, and a significant increase in speed cannot be desired.

In the description in FIGS. 17 and 18 and the method proposed by the same applicant, it is assumed that the central laser beam # 2 is incident on the Z axis. In each of the above-mentioned conventional methods, at least one laser beam must pass through the optical axis (Z axis) accurately without being deflected. However, in practice, it is very difficult to adjust the laser beam so that it is always on the Z axis (optical axis). For example, it is inevitable that the optical axis slightly fluctuates due to a change over time or a change in temperature of the apparatus.

[0021]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and without increasing the number of rotating components,
Provided is a cylindrical inner surface scanning type image recording device that can guide multiple light beams on a recording sheet with high accuracy with a simple configuration, realize high-speed recording, and has extremely easy optical system adjustment and easy handling. The purpose is to do.

[0022]

According to the present invention, an object of the present invention is to record an image by scanning a recording sheet held on the inner surface of a cylinder with a plurality of light beams modulated in accordance with image information and recording an image. A light beam output means for outputting the plurality of light beams; a multiplexing optical system for guiding the plurality of light beams substantially along the center axis of the cylinder; and a rotation axis for the center axis of the cylinder. By having a reflecting surface to be, by reflecting the plurality of light beams by the rotating reflecting surface,
Scanning means for performing main scanning on the recording sheet; light deflecting means for independently and one-dimensionally deflecting all of the plurality of light beams to cause displacement in the sub-scanning direction on the recording sheet; Control means for controlling the displacement positions of the plurality of light beams on the recording sheet by means in synchronization with the rotation of the reflection surface. Is done.

Another object of the present invention is to provide a cylindrical inner surface scanning type image recording apparatus which scans a recording sheet held on the inner surface of a cylinder with a plurality of light beams modulated in accordance with image information and records an image. A light beam output means for outputting a light beam; a multiplexing optical system for guiding the plurality of light beams substantially along the central axis of the cylinder; and a reflecting surface having the central axis of the cylinder as a rotation axis. A scanning unit that performs main scanning on the recording sheet by reflecting the plurality of light beams by the rotating reflecting surface; and all of the plurality of light beams are independently two-dimensionally deflected. Light deflecting means for causing displacement in the main scanning direction and sub-scanning direction on the recording sheet; and synchronizing displacement positions of the plurality of light beams on the recording sheet by the light deflecting means with rotation of the reflection surface. Let me control Control means for the; cylindrical inner surface scanning type image recording apparatus characterized by comprising also achieved by.

The light deflecting means may be a light deflecting element provided separately for each of the plurality of light beams. Further, the light deflecting element for one of the light beams may be omitted, and another light deflector may be provided at a position where the light beam after multiplexing all the light beams by the multiplexing optical system is deflected. Further, it is preferable to provide a correction means for correcting the curvature or interval of the main scanning line of each light beam.

This correcting means can confirm the scanning result on the recording sheet and manually input an appropriate correction amount to the control means. A light beam position detecting means may be provided on the inner surface of the cylinder substantially along the main scanning line, and the curvature and interval of the main scanning line may be automatically or manually corrected based on the detection result.

[0026]

According to the present invention, the light deflecting means is controlled based on a control signal from the control means, and a plurality of light beams output from the light beam output means and incident on the scanning means are independently and one-dimensionally deflected. . In this way, the curvature of the scanning lines of the plurality of light beams reflected by the scanning unit is corrected and guided on the recording sheet. In this case, since the rotating component is only the scanning unit, the accuracy can be easily improved.

In the present invention, the light deflecting means is controlled based on a control signal from the control means, and a plurality of light beams output from the light beam output means and incident on the scanning means are independently and two-dimensionally deflected. Let it. In this way, the curvature of the scanning lines of the plurality of light beams reflected by the scanning unit is corrected and guided on the recording sheet. In this case, a high-precision image can be recorded with the scanning line intervals being constant and the lengths being the same.

[0028]

FIGS. 1 and 2 are diagrams for explaining the principle of a first embodiment of the present invention, FIG. 3 is a diagram showing an output result thereof, and FIG. 4 is a diagram for explaining a trajectory of a light beam. It is.
First, the principle will be described with reference to these drawings. Here, it is assumed that the three laser beams # 1, # 2, and # 3 are incident on the YZ plane and parallel to the Z axis as in the case of FIG.

When the reflecting surface 4 of the optical scanner 2 is in the direction shown in FIG. 1 (the short axis of the reflecting surface 4 coincides with the Y axis), the laser beam L0 incident on the center of the reflecting surface 4 along the Z axis is , X-axis. Then, when this laser beam L0 is deflected by + θ _{X in the} X-axis direction with respect to the optical scanner 2, the reflected laser beam L0 becomes in the X · Z plane.
Displaced by −ΔZ in the Z direction. Further, the laser beam L0
Is displaced by −θ _{X in the} X-axis direction with respect to the optical scanner 2, the reflected laser beam L0 is displaced by + ΔZ in the Z direction in the X · Z plane.

Therefore, the laser beams # 1, # 2, and # 3 incident on the optical scanner 2 are respectively changed in the Y-axis direction (the direction orthogonal to the YZ plane which is a common plane including three laser beams). The laser beams # 1, # 2, and # 3 reflected can be deflected in the Z-axis direction by deviating in the minus direction and the positive direction of the X-axis by a predetermined amount while being separated from each other by a predetermined amount. . Therefore, the reflected laser beams # 1, # 2, and # 3 are substantially rotated about the X axis from the arrangement on the XY plane shown in FIG.
It can be set at a fixed distance in the axial direction.

Similarly, when the reflecting surface 4 of the optical scanner 2 is oriented in the direction shown in FIG. 2B, the laser beam # 1 is displaced by a predetermined amount in the plus direction of the X axis, and the laser beam # 3 is displaced.
By a predetermined amount in the negative direction of the X axis,
The reflected laser beams # 1, # 2, and # 3 are substantially rotated about the X axis from the arrangement on the XY plane shown in FIG. 17C,
As shown in FIG. 2B, it can be set at a certain distance in the Y-axis direction.

In FIGS. 1 and 2, the center laser beam # 2 is shown as being on the optical axis (Z axis) of the optical scanner 2. However, in fact, all laser beams # 1, #
Both # 2 and # 3 may deviate from the optical axis (Z axis). Therefore, in the present invention, all the laser beams # 1, #
2. By deflecting the incident direction of # 3 in the X-axis direction, the main scanning lines due to these are corrected to straight lines on the recording sheet S. At the same time, the interval between the main scanning lines is also corrected.

As described above, by adjusting the incident directions of the laser beams # 1, # 2, and # 3 on the reflecting surface 4 in the X direction in a one-dimensional manner, each of the laser beams # 1, # 2 on the recording sheet S is adjusted. , # 3 can be corrected to make them straight. Further, these scanning intervals can be made constant regardless of the scanning position. Therefore, FIG.
As shown in (1), the scanning lines recorded on the recording sheet S by the laser beams # 1, # 2, and # 3 can be formed as straight lines that are parallel over the entire scanning area.

Here, in the above description, it is assumed that the center laser beam # 2 is placed on the Z axis and the beam intervals are equal. At this time, as shown in FIG. 4A, the laser beams # 1, # 2, #
It is assumed that the spot No. 3 is projected onto a plane (conjugate plane) S ′ that is conjugate with the recording sheet S. Laser beam # 1 on the conjugate plane S 'accompanying rotation of the optical scanner 2
The locus of # 3 is as shown in FIG. 4B. That is, assuming that the angular velocity of the optical scanner 2 is ω, a simple vibration represented by the following equation is obtained.

[0035]

X = −a · cosωt: locus of laser beam # 1 X = a · cosωt: locus of laser beam # 3

Therefore, by deflecting the laser beams # 1 and # 3 according to the above equations and guiding them to the optical scanner 2, as shown in FIG. Can be formed.

Here, three laser beams # 1, # 2, and #
Let us consider a case where both 3 are deviated so as to be farther away from the optical axis (Z axis). FIG. 5 shows laser beams # 1, # 2, #
5A shows a case where the plane including 3 includes the optical axis (Z-axis) of the optical scanner 2, and FIG. 5A shows the beam arrangement viewed from the Z-axis direction.
FIG. 5B is a cross-sectional view along the YZ plane.

If the reflecting surface 4 is at the position shown by the solid line in FIG. 5B, the laser beams # 1 to # 3 are reflected in the + Y direction,
The reflected lights # 1 to # 3 are separated so as to be farther in order in the -Z direction. When the reflecting surface 4 is rotated by π radians and located at a position indicated by a virtual line, the laser beams # 1 to # 3 are reflected in the −Y direction, and the reflected lights # 1 to # 3 are distant in the + Z direction in order.

Therefore, in this case, the laser beam # 1,
A few simple vibrations in the Z-axis direction have respective amplitudes of b1,
As b2 and b3, b1cosωt, b2cosωt, b3co
It is represented by sωt. In some cases, the plane including the laser beams # 1 to # 3 does not include the optical axis (Z axis). In this case, the amplitude changes with the rotation angle (ωt) of the optical scanner 2 or the phase of cosωt changes. Change. Therefore, it is sufficient to express the equation of simple vibration in consideration of these, and it is not essentially different.

[0040]

FIG. 6 is a conceptual diagram showing a cylindrical inner surface scanning type image recording apparatus according to a first embodiment. In FIG. 6, reference numeral 6 (6a, 6b, 6c) denotes three laser diodes as light beam output means, which output laser beams L (La, Lb, Lc) having the same wavelength and the same intensity. These laser beams La, Lb, Lc are respectively applied to a collimating lens L1 (L1a, L1b, L1).
c) One-dimensional acousto-optic deflection element AOD (AODa, AO
Db, AODc), AOD exit lens L2 (L2a, L2
2b, L2c), zero-order optical cut plate P1 (P1a, P1
b, P1c) and a collimating lens L3 (L3a, L3
3b, L3c), and are multiplexed by the multiplexing optical system 8.

The laser beam L (La, Lb, Lc)
Are collimated by the collimating lens L1, are deflected by the AOD, and are collimated by the AOD exit lens L2 and the zero-order light cut plate P.
At 1, only the first-order diffracted light is selected. Then, the light is returned to a parallel light again by the collimating lens L3, and is guided to the multiplexing optical system 8.

As will be described later, the AOD is driven by the generation of an ultrasonic wave of a predetermined frequency from the transducer in response to the turning on of the binary image signal.
This is selected by the next light cut plate P1. When the binary image signal is off, the output of the laser diode 6 is off.

In this embodiment, the three AODs change the laser beams La, Lb, Lc one-dimensionally in the X-axis direction in FIG. That is, as described above, the three laser beams La, Lb, and Lc are multiplexed by the multiplexing optical system 8. However, when the AOD is driven at the above frequency, these laser beams L share a common plane (FIG. 2). (YZ plane). In this embodiment, the laser beam L is modulated in the direction (X-axis direction) orthogonal to the common plane (YZ plane) by modulating the driving frequency of the AOD based on the principle described with reference to FIGS.
To correct the curvature and interval of the main scanning line.

The multiplexing optical system 8 is formed by a total reflection mirror M, a polarizing beam splitter PBS, and a beam splitter BS. The laser diodes 6a, 6b, 6c output linearly polarized laser beams, and their polarization directions are set in directions indicated by arrows in FIG.

That is, the laser diodes 6a and 6c
The plane of vibration of the electric field of the plane wave incident on the beam splitter BS and the total reflection mirror M is polarized light (P-polarized light) parallel to the incident plane (plane including incident light and reflected light).
The mounting angle is set. The mounting angle of the laser diode 6b is set such that the plane of vibration of the electric field of the plane wave incident on the polarization beam splitter PBS is polarized perpendicular to the plane of incidence (S-polarized light).

The laser beams La, Lb, and Lc are multiplexed into almost one laser beam Lo by the multiplexing optical system 8. The combined laser beam Lo is shown in FIG.
In FIG. 2, it is shown as one beam, but in actuality, FIGS.
As shown in FIG. 5, the beam consists of three non-coaxial beams separated from each other.

The beam diameter of the combined laser beam Lo is further expanded and changed in the beam expander lenses L ₄ and L ₅ . Thereafter, removal of flare light (stray light) and control of the light beam diameter are performed in the aperture plate P2. This beam Lo is guided into the drum D along the center axis of the drum (cylinder) D. On the center axis of the drum D, a spinner SP as an optical scanner is provided.

This spinner SP has a reflection surface (reflection surface 4 in FIGS. 1 to 5) at 45 ° to the center axis (rotation axis), and is rotated at a high speed by a motor. A rotary encoder EN is attached to this motor, and a spinner SP
Is detected (θ = ωt). That is, a pulse signal p output at every predetermined rotation angle and a reference position signal p0 indicating a reference position of one rotation are output. Incidentally beam L guided to the spinner SP is through the focusing lens L _6, which is on the rotation axis, is focused on the inner peripheral surface or the recording sheet S of the drum D.

In FIG. 6, reference numeral 10 denotes control means.
The AOD is controlled in synchronization with the rotation angle θ of the spinner SP. Reference numeral 12 denotes when the control means 10 controls the AOD.
This is correction means for setting the correction amount of the curvature and interval of the main scanning line. The correcting means 12 looks at the output result of the main scanning line output on the recording sheet S, for example, and determines the radii a, b ₁ to b shown in FIG. 4B and FIG. ₃ and the amount of periodic variation of these radii are manually input.

FIG. 7 is a diagram showing an example of a circuit configuration of the control means 10. In FIG. 7, reference numeral 14 denotes a clock circuit.
On the basis of the pulse signal p and the reference position signal po output by the encoder EN at every constant rotation angle of the spinner SP,
The control clock signal CL (CLa, CLb, CLc) is output. Reference numeral 16 (16a, 16b, 16c) denotes three cosine wave generation circuits, which output cosine wave signals X (Xa, Xb, Xc) synchronized with the corresponding control clock signal CL.

As described above, these cosine wave signals X are
This is a correction amount to be added to the driving frequency of the AOD to deflect the laser beam L in the X-axis direction in order to correct the curvature and interval of the main scanning line. The data related to the amplitudes a, b1, b2, and b3 of the cosine wave signal X and the periodic changes in the amplitudes are input from the correction unit 12 in advance.

Reference numeral 18 (18a, 18b, 18c) denotes a voltage controlled oscillator (VCO), and a frequency modulation signal F (Fa, F) whose frequency changes in response to a voltage change of the cosine wave signal X.
b, Fc). This signal F is separately amplified by an amplifier (AMP) 24 (24a, 24b, 24c), and then guided to a corresponding AOD.

Reference numeral 20 denotes a binary image signal generation circuit for writing three main scanning lines to be recorded with three laser beams L based on an image signal input from an image processing circuit (not shown). Output a value image signal. These binary image signals are input to the laser diode 6 (6a, 6b, 6c). As a result, each laser diode 6 emits a laser beam when the binary image signal is on, and each AOD
The first-order diffracted light of the laser beam L is deflected from the YZ plane so as to be deviated in the X-axis direction by a correction amount corresponding to the cosine signal X.

As a result, three linear main scanning lines as shown in FIG. 3 can be recorded on the recording sheet S at equal intervals. In FIG. 3, the spinner SP is rotated by half a rotation (0 to π).
(Radian) only. The reason why the lengths of the three main scanning lines are different is that the deviation amounts of the three laser beams L from the rotation axis (optical axis Z axis) of the spinner SP are different.

The main scanning lines having different lengths correspond to the clock signals CL (CLa, C
Lb, CLc) can be made the same length by giving a phase difference. FIG. 8 shows a clock correction circuit 26 used for this purpose. This circuit 26 is a clock circuit 14
include.

In FIG. 8, reference numeral 28 denotes a PLL circuit, which outputs a phase synchronization signal based on a pulse signal p output from the encoder EN. Reference numeral 30 denotes a basic clock signal generation circuit, which generates a basic clock signal B based on the phase synchronization signal output from the PLL circuit 28 and the reference position signal po derived from the encoder EN.

Reference numeral 32 denotes a counter which counts the basic clock signal B. Reference numeral 34 denotes a look-up table (LUT) which stores in advance a delay amount of the control clock signals CLa, CLb, CLc for controlling the three laser beams L (# 1, # 2, # 3) according to the count value of the counter 32. doing. These delay amounts are determined for each laser beam L.
Varies with the amount of deviation from the optical axis (Z axis) and the rotation angle of the spinner SP.

Numeral 36 (36a, 36b, 36c) is a delay circuit, which delays the basic clock signal B by the delay amount obtained by the LUT 34 and controls the control clock signals CLa, C
Lb and CLc are output. These control clock signals C
L is sent to the binary image signal generation circuit 20 (FIG. 7),
A binary image signal is output to each laser diode 6 in synchronization with the signal CL.

[0059]

[Operation of the First Embodiment] The cylindrical inner surface scanning type image recording apparatus of the first embodiment is basically configured as described above. Next, the operation will be described.

The three laser beams L, which are turned on / off in accordance with image information and output from the laser diode 6 as light beam output means, are deflected in the X-axis direction by the respective acousto-optic elements AOD ( (See FIG. 5). 3
After the laser beam L is multiplexed by the multiplexing optical system 8, the laser beam L is introduced into a spinner SP as an optical scanner via a condenser lens L6. The spinner SP reflects and deflects the laser beam Lo by the reflecting surface 4 rotating about the Z axis, and guides the laser beam Lo to the recording sheet S. Then, as shown in FIG. 3, an image is formed on the recording sheet S by three linear scanning lines at regular intervals.

Next, the operation of the control means 10 will be described in detail with reference to FIGS. FIG. 9 is a timing chart of the clock correction circuit 26.

First, based on the pulse signal p from the encoder EN provided in the spinner SP and the reference position signal po for obtaining the main scanning start position, the clock circuit 14
Converts the control clock signal CL into a cosine wave signal generation circuit 16
a, 16b and 16c. Cosine wave signal generation circuit 1
6a, 16b, and 16c output cosine wave voltage signals to each VCO 1
8a, 18b and 18c.

The VCO converts the cosine wave voltage signal X into a frequency modulation signal F. The converted frequency modulation signal F is supplied to the acousto-optic devices AODa, AODb, and AODc via the amplifiers 24a, 24b, and 24c.
The laser beam L on / off controlled by the value image signal is deflected. In this case, the acousto-optic element AOD outputs the laser beams La, Lb,
Lc is deflected in the X-axis direction shown in FIG. 2 or FIG.

Now, the center laser beam Lb has an optical axis (Z axis).
If the intervals between the laser beams La, Lb, and Lc are constant, the laser beams La and Lc guided to the reflection surface 4 of the spinner SP are synchronized with the rotation of the spinner SP, as shown in FIG. As shown in the figure, a simple vibration occurs in the X-axis direction. At this time, the two laser beams La and Lc oscillate in a simple manner as shown in FIG. 4B in a state where the phases are shifted from each other by 180 ° (π radians).

At this time, the laser beam Lb is guided onto the recording sheet S without a single oscillation. And
As shown in FIG. 3, laser beams # 1, # 2, and # 3 whose intervals are controlled to be constant are guided to the recording sheet S, and an image is recorded. In this case, the interval is determined by the amplifier 24.
a, 24b, and 254c.

The three laser beams L (# 1, # 2, #
If all 3) are deviated from the optical axis (Z axis), 3
All the laser beams L vibrate in a simple manner. Therefore, in this case, the three laser beams L are all converted to the cosine wave signal generation circuit 16.
Of course, it is necessary to be deflected in the X-axis direction by a, 16b and 16c.

Here, each of the laser beams # 1, # 2, # 3
Is controlled so as to be deflected only in the X-axis direction, as shown in FIG. 3, since the scanning start position and the scanning end position are different, the length of each scanning line is different, and when the difference is large, There is a possibility that distortion of the image may be visually recognized.
However, such a problem can be solved by adjusting the output timing of the binary image signal using the control clock signals CLa, CLb, CLc generated by the control clock correction circuit 26 shown in FIG.

That is, the phase of the pulse signal p sent from the encoder EN is controlled by the PLL circuit 28 to generate a phase synchronization signal. This phase synchronizing signal is supplied to the basic clock signal generating circuit 30, where the basic clock signal B shown in FIG. 9 is generated at a timing determined by the reference position signal po indicating the main scanning start timing supplied from the encoder EN. Is done. The basic clock signal B is counted by the counter 32,
It is supplied to delay circuits 36a, 36b, 36c. The count value of the basic clock signal B counted by the counter 32 is supplied to the look-up table 34.

The look-up table 34 stores the laser beams # 1, # 2, and # in accordance with the count value.
In response to the scanning position of the third recording sheet S, a preset delay amount setting signal is output to each of the delay circuits 36a, 36b, 3
6c. Each of the delay circuits 36a, 36b, 36
c delays the basic clock signal B from the basic clock signal generation circuit 30 by a predetermined amount based on the delay amount setting signal, and sets the control clock signals CLa, CLb, and CLc to 2
It is supplied to the value image signal generation circuit 20.

In this case, the control clock signal CLa
Is a signal for controlling the output timing of the binary image signal recorded on the recording sheet S by the laser beam # 1, and based on the delay amount setting signal from the lookup table 34, as shown in FIG. The circuit 36a delays the recording start timing of the image based on the binary image signal by Td1 from the basic clock signal B, and adjusts the recording end timing to the main scanning end timing (m-th clock signal) of the basic clock signal B. To set. The interval between the pulses of the control clock signal CLa is set to be as equal as possible by the delay amount setting signal from the look-up table 48.

The control clock signal CLb is a signal for controlling the output timing of the binary image signal recorded on the recording sheet S by the laser beam # 2. As shown in FIG. Based on the delay amount setting signal, the delay circuit 36b delays the recording start timing of the image based on the binary image signal by Td2 from the basic clock signal B, and sets the recording end timing to the main scan end timing of the basic clock signal B ( It is set to be delayed by Td2 from the (m-th clock signal). The intervals between the pulses of the control clock signal CLb are set to be as equal as possible by the delay amount setting signal from the lookup table 34.

Further, the control clock signal CLc is a signal for controlling the output timing of the binary image signal recorded on the recording sheet S by the laser beam # 3, and as shown in FIG. The delay circuit 36c sets the image recording start timing based on the binary image signal to the same as the main scanning start timing of the basic clock signal B, and sets the recording end timing based on the basic clock signal B main scanning. It is set with a delay of Td3 from the end timing (m-th clock signal). The interval between the pulses of the control clock signal CLc is set to be as equal as possible by the delay amount setting signal from the lookup table 34.

In this case, if the delay positions between the adjacent scanning lines overlap with each other, a beat may be generated between the scanning lines and the halftone dot, resulting in an uneven image. It is desirable that the signal is set so as to be random between the scanning lines.

The control clock signals CLa, CLb, CLc set as described above are supplied to the binary image signal generation circuit 20, and the binary image signals are supplied to the laser diodes 6a, 6b at the respective timings shown in FIG. , 6c.
In this case, the laser beams # 1, # 2, and # 3 modulated based on the binary image signal are used to record an image on the recording sheet S in the same recording range as the laser beam # 3 (see FIG. 3).
Will be recorded. Therefore, it is possible to form a high-precision image having the same recording range of the image in the main scanning direction and no distortion.

In the first embodiment described above, the difference in scanning line length due to the laser beams # 1, # 2, and # 3 on the recording sheet S is eliminated by adjusting the respective recording timings. By adopting the second embodiment shown in (1), the interval and length of the scanning lines can be made constant. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

[0076]

Second Embodiment FIGS. 10 to 13 are views for explaining the principle of a second embodiment of the present invention. In this embodiment, when the three laser beams L (# 1, # 2, # 3) are not on a common plane and none of them is on the optical axis (Z axis), each laser beam L is independently controlled. It deflects two-dimensionally.

First, when the reflecting surface 4 of the optical scanner 2 is in the direction of FIG. 10A (the short axis of the reflecting surface 4 coincides with the Y axis), the laser beam incident on the center of the reflecting surface 4 along the Z axis When the incident direction of the laser beam Lo with respect to the optical scanner 2 is deviated by −θ _{X in the} X axis direction, the reflected laser beam Lo is deflected by + ΔZ in the Z direction in a predetermined plane orthogonal to the X axis. Rank.

As shown in FIG. 10B, when the laser beam Lo is displaced by + θ _{Y in the} Y-axis direction with respect to the optical scanner 2, the reflected laser beam Lo becomes a predetermined surface orthogonal to the X-axis. In the Y direction by + Δy.
Therefore, as shown in FIG.
By displacing θ _{XY in the} Y-axis direction, the reflected laser beam Lo can be two-dimensionally displaced on the recording sheet S.

Therefore, the laser beam # 1 is displaced by a predetermined amount in the minus direction of the X axis and the plus direction of the Y axis, and the laser beam # 3 is shifted by a predetermined amount in the plus direction of the X axis and the minus direction of the Y axis. 11A, the focal points of the reflected laser beams # 1, # 2, and # 3 on the recording sheet S are changed from the arrangement on the XY plane shown in FIG.
It is possible to correct the array along the Z-axis direction on the XZ plane shown in FIG.

Similarly, the reflection surface 4 of the optical scanner 2 is
, The laser beam # 1 is deflected by a predetermined amount in the plus direction of the X axis and the plus direction of the Y axis, and the laser beam # 3 is shifted by a predetermined amount in the minus direction of the X axis and the minus direction of the Y axis. By deviating, the condensing points of the reflected laser beams # 1, # 2, and # 3 are changed as shown in FIG.
FIG. 1C shows an arrangement along the Z-axis direction on the XY plane shown in FIG. 7C.
The arrangement can be modified to the arrangement on the XZ plane shown in FIG. 1B.

As described above, by adjusting the incident directions of the laser beams # 1 and # 3 on the reflecting surface 4 two-dimensionally, each of the laser beams # 1 and # 3 on the recording sheet S can be adjusted.
The spots # 2 and # 3 can always be arranged in the Z-axis direction. Therefore, as shown in FIG. 12, the scanning lines recorded on the recording sheet S by the laser beams # 1, # 2, and # 3 can be formed as parallel straight lines over the entire scanning area, and the scanning can be performed. The line lengths can be the same.

Here, in the above description, the center laser beam # 2 is placed on the Z axis, and the three laser beams # 1, # 2, and # 3 are on a common plane and the beam intervals are equal. Consider the case. At this time, as shown in FIG. 13A,
Laser beams # 1, # incident on the reflecting surface 4 of the optical scanner 2
When the spots # 2 and # 3 are projected on a plane S ′ conjugate with the recording sheet S, the trajectories of the laser beams # 1 and # 3 on the conjugate plane S ′ due to the rotation of the optical scanner 2 are 13B, the angular velocity of the optical scanner 2 is ω, and the circle is represented by the following equation.

[0083]

X = −a · cosωt Trajectory of laser beam # 1 Y = −a · sinωt Trajectory of laser beam # 1 X = a · cosωt Trajectory of laser beam # 3 Y = a · sinωt Trajectory of laser beam # 3

Therefore, by deflecting the laser beams # 1 and # 3 according to the above equations and guiding them to the optical scanner 2, a plurality of scanning lines having a constant interval are formed as shown in FIG. can do.

Here, three laser beams # 1, # 2, and #
It is assumed that all 3 are not on the Z axis, not on the same plane, and the beam interval is not constant. FIG. 14 is a diagram showing an example of the beam arrangement in this case as viewed from the Z-axis direction. As described above, it is assumed that the laser beams # 1, # 2, and # 3 are apart from the Z axis (the rotation axis and the optical axis of the optical scanner 2) by c1, c2, and c3, respectively, and have a phase difference.

In this case, the beam trajectory on the conjugate plane corresponding to FIG. 13B is a concentric circle. Accordingly, a circle equation having different radii and phases for the three laser beams # 1, # 2, and # 3 is obtained. If each of the laser beams # 1, # 2, and # 3 is deflected and guided to the optical scanner 2 according to these equations, a main scanning line composed of three straight lines having a constant interval as shown in FIG. Is obtained.

Note that the center of the optical scanner 2 may rotate around the Z axis with the rotation. In this case, the beam trajectory on the conjugate plane corresponding to FIG. 13B has a shape such as an ellipse, but at this time only the above equation changes,
Not essentially different.

The second embodiment can have substantially the same configuration as the first embodiment shown in FIG. 6, except that the AOD can deflect two-dimensionally. These two-dimensionally deflectable AODs are driven by control means 100 shown in FIG. Although FIG. 15 shows a drive circuit of only one AODa for the sake of simplicity of explanation, a circuit similar to FIG.
Provided separately for AODc.

In FIG. 15, 116a (A) is a sine wave signal generation circuit, and 116a (B) is a cosine wave signal generation circuit. Reference numeral 112 denotes a correction unit that sets the amount of deflection in the X direction and the Y direction necessary to make the main scanning lines straight at equal intervals and length as described above.

The voltage controlled oscillators 118a (A) and 118a (B) output frequencies corresponding to the output voltage of the sine wave signal generation circuit 116a (A) and the output voltage of the cosine wave signal generation circuit 116a (B), respectively. (VCO). The output of the oscillator 118a (A) is an amplifier (AMP) 124a
The signal is input to the deflection electrode in the X-axis direction of AODa through (A). The binary image signal output from the binary image signal generation circuit 20 turns the laser diode 6 on and off.

The output of the oscillator 118a (B) is
MP) 124a (B), and is input to the deflection electrode in the Y-axis direction of AODa. Similarly, high-frequency signals for performing deflection in the X-axis direction and the Y-axis direction are input to the other AODb and AODc, respectively.

[0092]

FIG. 16 is a conceptual diagram of another embodiment. This embodiment comprises three AODs (AODa, AOD
b, AODc), one of the AODa
It was moved to the downstream side of.

Therefore, the drive frequency of the AODa is corrected by the eccentricity of the optical scanner 2 (spinner SP) and the aging of the optical system (lenses L4, L5, L6, etc.) of the combined laser beam L, and the deviation due to temperature change. By adding such correction, the combined laser beam L can be easily corrected. Here, the AOD may perform one-dimensional deflection (the first embodiment) or may perform two-dimensional deflection (the second embodiment).

In the embodiment shown in FIG.
Numeral 12 automatically inputs a correction coefficient or the like to the control means 200. That is, the drum 212 has a sensor 212A as a light beam position detecting means for detecting a main scanning line.
Was provided. Based on the output of the sensor 212A, the correction unit 212 detects the magnitude, period, and interval of the curvature of the main scanning line, and obtains coefficients and variables used in the above-described equation for determining the deflection amount.

Such automatic correction can be performed automatically at a predetermined time, such as when the power of the apparatus is turned on or when a predetermined time has elapsed. When the operator presses a switch for instructing automatic correction at an appropriate time,
It may be performed.

In the above-described second embodiment, the AOD is configured to realize deflection in the X-axis and Y-axis directions and modulation in accordance with image information by one acousto-optic element. However, it is also possible to use a combination of two one-dimensional acousto-optic elements that perform deflection in the X-axis direction and the Y-axis direction. In each embodiment, an electro-optic element may be used instead of using an acousto-optic element. Alternatively, four or more laser beams may be generated and independently deflected according to the present invention to record an image.

If the amount of deflection of the laser beams # 1, # 2, and # 3 by the acousto-optic element AOD is configured to be switchable, a cylindrical inner surface scanning type image recording apparatus with variable image resolution can be obtained. Further, the cosine wave signal generation circuits 16a and 116a (B) and the sine wave signal generation circuit 116a
By adding a correction signal to each signal output from (A), the aberration of the condenser lens Lo, the distortion of the reflection surface 4 of the optical scanner 2, the fluctuation of the rotation axis of the optical scanner 2, the optical scanning Vessel 2
As described above, it is possible to correct the distortion of the scanning line when the laser beams # 1, # 2, and # 3 are incident obliquely or offset with respect to the rotation axis.

[0098]

As described above, according to the first aspect of the present invention, since the movable portion is only the scanning means, no mechanical adjustment is required, and the accuracy can be easily improved. Further, it is possible to make the whole apparatus compact. further,
Since each light beam is one-dimensionally deflected, the curvature of the scanning line can be corrected to be a straight line, and the interval between the scanning lines can be adjusted. Therefore, high-precision image recording can be easily realized by electrical control.

According to the second aspect of the present invention, all the plurality of light beams are independently and two-dimensionally deflected, so that the scanning lines can be linearized and their intervals and lengths can be simultaneously adjusted. .

Further, according to these inventions, it is possible to easily expand from the conventional type in which one light beam is deflected by an optical scanner to record an image, to the type using a plurality of light beams of the present invention. It is possible. In addition, since the number of light beams can be easily increased, especially an increase of three or more, for example,
By setting the number of rotations of the scanning unit to be low, it is also possible to improve the reliability of recording accuracy by scanning.

The light deflecting means can be constituted by a light deflecting element provided for each light beam so as to deflect the light beams separated independently before being collected by the multiplexing optical system. ). One of these light deflecting elements may be moved to a position on the downstream side of the multiplexing optical system to deflect one collected light beam.
In this case, the influence of a change over time or a change in temperature of the optical scanner or the like can be conveniently corrected by the moved one light deflection element.

The control means may be provided with a correction means for correcting the curvature and interval of the main scanning line from the recording result of the main scanning line. For example, a configuration may be adopted in which the degree of curvature of each main scanning line and the degree of irregularity of the intervals are measured while observing the recording result output on the recording sheet, and the correction coefficient is manually input. Light beam detecting means for detecting the curvature and interval of the main scanning line is provided on the inner surface of the cylinder,
The correction may be automatically performed based on the detection result (claim 6). The light deflecting element can be an acousto-optical element (claim 7).

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of an embodiment of the present invention.

FIG. 2 is a diagram illustrating the principle of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a recording result of a main scanning line on a recording sheet according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a trajectory of a light beam on a plane conjugate with a recording sheet in the first embodiment.

FIG. 5 is a view for explaining another arrangement example of the light beam.

FIG. 6 is a configuration diagram of a first embodiment of a cylindrical inner surface scanning type image recording apparatus.

FIG. 7 is a circuit configuration diagram of a first embodiment of a cylindrical inner surface scanning type image recording apparatus.

8 is a configuration diagram of a control clock signal generation circuit in the control circuit shown in FIG.

FIG. 9 is a timing chart of a control clock signal.

FIG. 10 is a diagram illustrating the principle of a second embodiment of the present invention.

FIG. 11 is a diagram illustrating the principle of the second embodiment of the present invention.

FIG. 12 is an explanatory diagram of scanning lines on a recording sheet according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram of a trajectory of a light beam on a plane conjugate with a recording sheet in the second embodiment.

FIG. 14 is a view for explaining another example of arrangement of a light beam.

FIG. 15 is a circuit configuration diagram of a second embodiment of a cylindrical inner surface scanning type image recording apparatus.

FIG. 16 is a configuration diagram of another embodiment of a cylindrical inner surface scanning type image recording apparatus.

FIG. 17 is an explanatory diagram in a case where deflection control of a light beam is not performed.

FIG. 18 is an explanatory diagram of a scanning line formed when light beam deflection control is not performed.

[Explanation of symbols]

 2 Optical Scanner as Scanning Unit 6 Laser Diode as Light Beam Output Unit 8 Combining Optical System 10, 100, 200 Control Unit 12, 112, 212 Modification Unit 212A Sensor as Light Beam Position Detection Unit AOD Light Deflection Unit Acousto-optic device SP Spinner as optical scanner D Drum S Recording sheet

Claims (7)

[Claims] 1. A cylindrical inner surface scanning type image recording apparatus for scanning a recording sheet held on an inner surface of a cylinder with a plurality of light beams modulated in accordance with image information and recording an image; A multiplexing optical system for guiding the plurality of light beams substantially along the central axis of the cylinder; and a reflecting surface having the central axis of the cylinder as a rotation axis; Scanning means for main-scanning the recording sheet by reflecting a plurality of light beams on the rotating reflecting surface; and independently and one-dimensionally deflecting all of the plurality of light beams on the recording sheet. A light deflecting means for causing a displacement in the sub-scanning direction with; a control means for controlling the displacement positions of the plurality of light beams on the recording sheet by the light deflecting means in synchronization with the rotation of the reflection surface; Characterized by having Cylindrical inner surface scanning type image recording device. 2. A cylindrical inner surface scanning type image recording apparatus which scans a recording sheet held on an inner surface of a cylinder with a plurality of light beams modulated in accordance with image information and records an image; A multiplexing optical system for guiding the plurality of light beams substantially along the central axis of the cylinder; and a reflecting surface having the central axis of the cylinder as a rotation axis; Scanning means for main-scanning the recording sheet by reflecting a plurality of light beams on the rotating reflecting surface; and deflecting all of the plurality of light beams independently and two-dimensionally. Light deflecting means for causing displacement in the main scanning direction and the sub-scanning direction above;
Control means for controlling displacement positions of the plurality of light beams on the recording sheet by the light deflecting means in synchronization with rotation of the reflection surface. . 3. The image recording apparatus according to claim 1, wherein the light deflecting means has a plurality of light deflecting elements for deflecting the light beams separated from each other before being multiplexed by the multiplexing optical system. apparatus. 4. An optical deflecting device, comprising: an optical deflecting element for deflecting another light beam except one of the separated light beams before being multiplexed by the multiplexing optical system; 3. A cylindrical inner surface scanning type image recording apparatus according to claim 1, further comprising one optical deflection element for deflecting the plurality of waved light beams. 5. The control device according to claim 1, further comprising a correcting unit configured to correct a curvature and an interval of each main scanning line based on the plurality of main scanning lines output on the recording sheet by the plurality of light beams. A cylindrical inner surface scanning image recording apparatus according to any one of 1 to 4. 6. A light beam position detecting means provided substantially along a main scanning line of a light beam on an inner surface of a cylinder, and a curvature and an interval of each main scanning line are corrected based on a detection result of the light beam position detecting means. The cylindrical inner surface scanning type image recording apparatus according to any one of claims 1 to 4, further comprising correction means for performing the correction. 7. The image recording apparatus according to claim 3, wherein the light deflecting element is an acousto-optic element.